Robotic-Assisted Debulking, Anatomy Measurement, and Stent Placement

Introduction

Complex percutaneous coronary intervention (PCI) is becoming common in the cath lab. These technically demanding cases can be long in duration, increasing the amount of scatter radiation to which the operator is exposed. Robotic-assisted PCI has emerged as a way to reduce operator exposure to scatter radiation as well as to decrease strain on the musculoskeletal system. Atherectomy devices used in contemporary PCI have not been studied for use with the CorPath Vascular Robotic System (Corindus Vascular Robotics). In this report, we demonstrate that excimer laser coronary atherectomy (ELCA) can be performed robotically to restore flow to severely stenosed vessels. 

History

A 74-year-old woman with a history of coronary artery disease (CAD), heart failure, myocardial infarction (MI), and unstable angina (UA) was referred for evaluation following increased frequency of exertional chest pain and shortness of breath. The patient was taking two anti-anginal medications. The patient’s medical history also included diabetes, hypertension, hyperlipidemia, chronic obstructive pulmonary disease, and melanoma. Diagnostic angiography showed long, segmental stenosis of 99% in the mid left anterior descending (LAD) artery, with a rise to a medium-sized diagonal branch (Figure 1). A previous stent in the left circumflex artery was patent. 

Procedure

The patient was consciously sedated and anticoagulation was achieved using intravenous bivalirudin. A Pilot 200 (Abbott Vascular) guidewire and an EBU 3.75 6 French (Fr) Judkins (Medtronic) guide catheter were introduced and advanced to the LAD. After multiple views, the guidewire was advanced to cross the stenosis. The operator then moved to the robotic interventional cockpit, and a scrub technologist loaded an ELCA 0.9 mm x 80 mm Vitesse RX (Spectranetics) laser catheter into the CorPath cassette, which is mounted on the bed rail of the patient table. Using the joystick on the control console, the operator moved the catheter forward. By using CorPath’s “turbo” feature, which doubles the movement speed indicated by the joystick position, the laser catheter was quickly advanced through the guiding catheter to the coronary anatomy. Thereafter, the robot advanced the laser catheter by 1 mm per second to the mid LAD. The laser made two passes across the segmentable stenosis until a good lumen had been created (Figure 2). The lesion was somewhat dilated, and the vessel was larger than anticipated. The laser catheter was robotically retracted into the guide, and a technologist removed the catheter from the CorPath cassette. 

At the bedside, the assisting physician manually introduced a 2.0 mm x 20 mm AngioSculpt (Spectranetics) scoring balloon. The balloon was inflated for 33 seconds at 12 atmospheres (atm) in the mid LAD. Images were obtained, and the balloon was re-inflated for 30 seconds at 12 atm, resulting in successful dilatation of the lesion (Figure 3). The primary physician seated at the robotic console viewed activity at the bedside via a monitor at the console. Advancement of the AngioSculpt balloon was also visible on the hi-definition flat panel monitor at the console. The lead-lined interventional cockpit is located just a couple of feet from the bedside, making it possible to “call” instructions regarding inflation and re-inflation of the balloon to the assisting physician. 

CorPath’s measurement feature was then used to determine the length of anatomy to treat. A Xience Alpine (Abbott Vascular) drug-eluting stent (2.25 mm x 28 mm) was selected and loaded in the CorPath cassette by a technologist. At the control console, the “turbo” feature was used to quickly advance the stent catheter through the guide up to the LAD. Using the robot, stent positioning was optimized and then manually deployed (Figure 4). Post-intervention images showed 0% stenosis and TIMI grade 3 flow (Figure 5), and the stent catheter was robotically retracted. The guidewire and guide catheter were removed, and an Angio-Seal (St. Jude Medical) closure device was deployed at the access site. 

There were no unexpected events during the procedure, which went smoothly. The patient is angina-free and continues on dual antiplatelet therapy of daily aspirin and clopidogrel. 

Discussion

There have been several recent reports of the adverse effects of chronic exposure to interventional fluoroscopy. The number of reported malignant brain tumors among interventionalists is now 43 (including 2 nurses).¹ Most of the tumors have been located in the left hemisphere¹, suggesting a clinical consequence to the significantly higher radiation directed to the left side of interventionalists’ heads as compared to the right side, demonstrated in the BRAIN study (106.1 mrad and 50.2 mrad, respectively, P<0.001).² Another clinical consequence is premature brain aging. Compared to non-interventional medical personnel, workers in the cath lab had lower scores on neuropsychological tests assessing left-hemisphere function, e.g., verbal long-term memory and fluency, and short-term visual memory (there were no differences in tests scores between the two arms on right-sided tasks). This is alarming, given the average age in the interventional cohort: 46 for men and 43 for women.³ In addition, results from the Healthy Cath Lab study suggest high-volume interventional personnel have a heightened risk for cardiovascular disease. High-volume interventional staff had significantly higher carotid intima-media thickness, a proxy for subclinical atherosclerosis, and significantly shortened leukocyte telomere length, a proxy for biological aging, than control despite the two groups being similarly aged (mean age 45 in the interventional arm vs 44 in control).⁴ Early onset of cataracts is another concern. In the endovascular arena, a recent study estimated that 23.4 hours of fluoroscopy is equivalent to the annual eye-dose limit of 20 mSv recommended by the International Commission on Radiation Protection.⁵ 

Robotic-assisted PCI is one way to reduce the operator’s exposure to fluoroscopy scatter and the concomitant health effects. The PRECISE study showed significantly lower radiation levels at the interventional cockpit compared to the patient table at 0.98 µGy and 20.6 µGy, respectively.⁶ In addition, being seated at the interventional cockpit may reduce orthopedic injury, which affects roughly half of interventionalists who spend many hours wearing leaded protective gear.⁷ 

Robotic-assisted PCI may also have a positive effect on patient outcomes. CorPath’s measurement tool aids in stent selection for a given lesion and optimizes stent placement. Inadequate stent coverage and geographic miss increases the risk of restenosis. Most operators visually assess the lesion length; however, a recent study showed that visual assessments were inaccurate for more than half of lesions.⁸ An analysis of propensity-matched subjects in the PRECISE and STLLR studies showed a significantly lower rate of longitudinal geographic miss (LGM) for patients treated with robotic-assisted PCI compared to those receiving manual PCI at 10.3% and 64.1%, respectively (P<0.0001).⁹ Prospective, longer-term studies are needed to confirm that significantly lower LGM translates to reduced restenosis, but the differential in LGM is notable.  

Robot plus laser makes a good combination. ELCA is a useful adjunctive tool for treating long or moderately calcified lesions as well as in-stent restenosis. Through the delivery of ultraviolet B (UVB) pulses and continuous saline flush, the excimer laser removes plaque and creates a lumen for a stent. The laser’s 308 nm wavelength has a shallow tissue depth, minimizing the risk of vessel perforation.^10,11 Our case demonstrates that an ELCA catheter can be integrated with the CorPath robot without damaging the ELCA’s optical fibers. The robot also removes any question as to the “right” pace of ELCA. When performing ELCA, it is not uncommon to wonder whether the laser catheter is being advanced too quickly or too slowly. When treating long lesions, it is critical to give the laser the time necessary to photoablate plaque. CorPath does this by advancing the laser catheter by 1 mm per second. 

Looking to the future. With more complex PCI cases on the rise, the use of robotic assistance may be preferable to other radiation reduction or protection methods, particularly since the robot also eases musculoskeletal strain for the operator. It is possible that the robot will improve patient outcomes either by lowering the rate of restenosis resulting from inaccurate visual assessment and geographic miss, or by encouraging physicians to perform more cases via radial access. Regarding the latter, a recent worldwide survey showed that almost half of interventional cardiologists would perform more radial PCI if the operator’s exposure to scatter radiation could be reduced.¹² In the CorPath PRECISION post-market registry, 57% of the cases were performed via radial access. Notably, radial access cases had lower average fluoroscopy time than femoral access cases.¹³ 

There are exciting areas that can be addressed by the combination of the robot and excimer laser. The robot and excimer laser may be the optimal method to implant bioabsorable stents by creating a good lumen and enhancing precise placement. In addition, the excimer laser is already used in peripheral vascular interventions (PVIs). Although currently off-label for CorPath, results from a feasibility study using CorPath in the endovascular treatment of peripheral artery disease demonstrated a 100% technical success rate for robotic-assisted PVI.¹⁴ This is just one area where CorPath could aid both the patient and the physician through precision and radiation reduction, respectively. We expect CorPath’s utility in interventions will expand over time as operators gain experience trying different catheters or techniques with the robot.

References

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Disclosures: Dr. Stanley Mannino and Dr. Cherian John report no conflicts of interest regarding the content herein.

The authors can be contacted via Dr. Stanley Mannino at scmannino@comcast.net